It is not an easy call. But to be guilty, one needs to have free will. How free is the will of someone who is seriously psychotic?

Let's start with the easy cases. Just having a mental illness cannot be grounds for acquittal. The illness may not be active when you carry out a crime. Or it may not be relevant to the crime. Just having a diagnosis -- and in recent decades they have proliferated ridiculously -- does not give you legal carte blanche.

So you need mental illness plus. Plus what? Texas law says, plus the inability to distinguish right from wrong.

The easy case here is the guy who is hallucinating and takes an ax to a skull thinking it is a pumpkin. You cannot possibly find this person guilty. He literally knows not what he does.

That does not mean he walks free. Anybody that crazy is obviously a danger to the community. He needs to be controlled, confined and supervised for as long as it takes until society is sure that he will not again mistake a head for a pumpkin.

The hard case occurs when the murderer seems to know what he is doing. In one sense, Andrea Yates obviously knew what she was doing when she drowned each of her five children slowly, horribly, deliberately. The jury found her guilty, concluding that her actions that day -- waiting until her husband had left home, calling the cops immediately after she had killed her children -- demonstrated that she knew the killings were wrong.

It is a plausible line of argument, but I would argue differently. She clearly knew that what she did was illegal. And prohibited. And would cause her to be punished. But in the grip of a fantastic psychosis, she actually thought it was right. She thought she was saving her children from a worse fate, in this world and the next.

That is her story, and I do not believe it is a post-hoc rationalization. It is simply too common in cases of maternal infanticide resulting from postpartum depression. The psychotic thinking is quite typical: The mother feels some terrible satanic evil enveloping her and her children. She feels compelled -- often ordered by voices or other hallucinatory forces -- to "save" the children from that overwhelming evil by killing them.

In some cases, the mother then kills herself as well, sparing us the conundrum of deciding her guilt. Andrea Yates did not. But she fits the classic pattern. Since the birth of her firstborn, Yates had had visions of a knife and blood and child-murder. She twice tried to commit suicide, and had told a psychologist, "I had a fear I would hurt somebody. I thought it better to end my own life and prevent it."

Said Dr. Eileen Starbranch, the psychiatrist who treated one of her postpartum depressions, "She would rank among the five sickest -- and most difficult to get out of psychosis -- people that I've ever treated." And while her psychosis could often be controlled by medications, her doctor had stopped her antipsychotics just weeks before the killings. Even the prosecution psychiatrist admitted that when interviewed the day after the killings, she was "grossly psychotic," telling the county jail psychiatrist that voices had told her to kill her children.

This is not to say that any criminal can rationalize his crime as being for some higher good. This extenuation only applies in the case of severe mental derangement. Andrea Yates was clearly mentally deranged, not as proved by the murders -- that would make the murders self-acquitting -- but as demonstrated by her noncriminal behavior: self-injury, severe withdrawal, bizarre behavior, occasional catatonia, delusion, hallucinations.

As a former psychiatrist, I found the film "A Beautiful Mind" brilliant in rendering to people who have never seen psychosis how compelling hallucinations can be. The movie substituted visual hallucinations (which are rare) for auditory hallucinations (which are far more common but less vivid on screen), but the idea is the same: These visions and voices are so powerful that they can be irresistible.

Andrea Yates's mental illness is now masked by the Haldol she should have been taking at the time of the murders. I find it hard to see how she can be deemed by society to be truly responsible for her crime.

This is not a matter of sympathy. I have infinitely more sympathy for the five innocents who died so terribly. This is a matter of justice. Guilt presupposes free will. Did Andrea Yates really have
it?